Ideally we do not repeat a full IG-SRT course on the same area. Once an area has received the complete prescribed radiation dose, that skin has essentially taken as much radiation as is safe for a lifetime for that spot. If a cancer in the exact same spot were to recur (which is quite rare, given the ~99% cure rates), the next step is usually surgery rather than another radiation course. Repeating radiation could risk serious damage to the skin and underlying tissue (like chronic ulcers or poor healing). So standard protocol is one-and-done for radiation on a given lesion/site. That being said, if by “repeat” one means treating multiple distinct lesions at different times on different parts of the body, then yes – IG-SRT can be repeated in the sense that you could treat new skin cancers with IG-SRT again. For example, if you had IG-SRT on your nose this year and everything went well, and two years later you get a new basal cell on your cheek, you can absolutely have IG-SRT on the cheek. There’s no limit to how many separate lesions on separate areas can be treated in your lifetime (aside from practical considerations like small cumulative scatter doses, but those are negligible). The limitation is only that the same exact field shouldn’t be radiated twice at full dose. If a recurrence or new tumor occurs overlapping an old field, we weigh other options more heavily. But for new lesions elsewhere, yes, IG-SRT can be “repeated” as a technique.
To clarify: If IG-SRT does not completely clear a tumor (which is very unlikely) or if that tumor regrows, usually surgery is done next (we wouldn’t just do another round of IG-SRT on it). However, fortunately, needing that is rare due to the high success initially. All of this underscores why we aim to get it right the first time with IG-SRT, and we rely on its excellent cure probability. So in practice, we seldom face re-treating the same spot with radiation. If you ever were in that scenario, we’d discuss the safest plan then. But as a general rule, no, the same area isn’t radiated twice with full courses; instead, other modalities would be employed on recurrence.
